Direct obsurvation of beauty particle decays and high statistic study of charm particles by the automatic measuring system with track selector
Grant-in-Aid for Specially Promoted Research
|Allocation Type||Single-year Grants |
|Research Institution||Nagoya University |
NIU Kiyoshi Professor, Faculty of Science, 理学部, 教授 (50013363)
HOSHINO Kaoru Research Associate, Faculty of Science, 理学部, 助手 (70022738)
NIWA Kimio Research Associate, Faculty of Science, 理学部, 助手 (60113445)
|Project Period (FY)
1983 – 1986
Completed (Fiscal Year 1986)
|Budget Amount *help
¥215,000,000 (Direct Cost: ¥215,000,000)
Fiscal Year 1986: ¥19,000,000 (Direct Cost: ¥19,000,000)
Fiscal Year 1985: ¥22,000,000 (Direct Cost: ¥22,000,000)
Fiscal Year 1984: ¥90,000,000 (Direct Cost: ¥90,000,000)
Fiscal Year 1983: ¥84,000,000 (Direct Cost: ¥84,000,000)
|Keywords||Charm particle / Beauty particle / Nuclear emulsion / Fully automated track selector / Emulsion tape / ハイブリッドバーテックス検出器 / 新素粒子測定装置 / 自動飛跡選別装置|
We have obtained outstanding results in the advanced experimental elementary particle physics; the direct observation of beauty particle decays and the study of charm particle production. The direct observation of the beauty and charm particles which contain heavy quarks in their constituents have been very difficult, because they are the extremely rare products in the high energy interactions, and because they have extremely short lifetimes of the order of 0.1-1 ps.
In this study, we adopted a hybrid apparatus which consists of stacks of nuclear emulsion plates and the various electronic detectors. Because of a very high spatial resolvinig power inherent in the emulsion, tracks of beauty and charm particles connecting the production and decay points are fully observed in the emulsion stack. To locate and analyse nuclear interactions with high efficiency, we have utilized a unique and powerful automatic track analysing system developed by ourselves with analysing power higher than 10,00
We have discovered following rare events, out of 3 x <10^8> interactions recorded in the emulsion target exposed to the 350 GeV <pi> <^-> beam in the CERN experiment WA75.
1) One event with the associated production of a pair of beauty particles both of which decayed into charm particles in the emulsion. The weighted mean flight time of the two beauty particles was measured to be 0.3 +0.2/-0.1 ps. This directly measured lifetime is shorter than that estimated by indirect method in the other experiments. Clearly, more events directly observed are urgently needed.
2) Two events with the simultaneous production of two pairs (four) of charm particles decaying in the emulsion. The measured rate of double to single charm pair production is about 1/100. The rather large observed production rate of the events with double charm pairs is in disagreement with the results of any current calculations. This stimulates the more detailed QCD studies on the hadronization mechanism of the heavy quarks.
The fully automated emulsion analysis system developed by the Nagoya University in the course of this study has greatly extended the adoptability of emulsion technique in the field of elementary particle physics. Less
Report (2 results)
Research Products (14 results)